Divine things happen when you combine sharp lemons, creamy cheese and sweet pastry. Serve as a dessert or with afternoon tea.
First you must remove the bitterness from the strips of lemon zest. To do this, place the water and sugar in a small pan over a moderate heat and stir until the sugar has dissolved. Stir in the lemon strips, raise the heat and bring to the boil. Reduce the heat and simmer for a couple of minutes. Drain, discard the liquid and dry the lemon strips on a kitchen cloth. Leave to cool.
Grease a 25cm (10 inch) loose-bottomed tart tin with a little butter, then dust it lightly with flour. Roll out the puff pastry thinly on a lightly floured work surface. Use to line the tin, making sure it comes slightly above the edge. Place in the fridge until you are ready to use.
Preheat the oven to 180 degrees. To make the filling, beat the egg yolks and sugar together with an electric beater until light and fluffy and doubled in volume. Add the lemon juice and butter and mix well. Stir in the sieved ricotta, sift the plain flour over the top and whisk well to remove and lumps.
In another bowl, whisk the egg whites until they form stiff peaks. Fold them into the lemon mixture, pour into the pastry case and arrange the lemon strips evenly on top. Bake for 40 minutes, until just set. Leave to cool, then gently remove the tart from the tin and transfer to a plate.